1. Field of the Invention
The present invention generally relates to a selectively plated substrate and, more particularly, to an apparatus for continuously masking selected areas of a metal web with a non-conductive coating. The masked web is then processible in an electroplating apparatus followed by stripping the maskant to produce a web having selectively plated and unplated areas. The present invention is particularly advantageous for plating narrow, well defined metal stripes on a metal web.
2. Prior Art
It is known to selectively electroplate a metal web with plated stripes by first applying a resist to the metal surface, plating the areas devoid of resist material and then removing the resist after the plating step. Several techniques are known for accomplishing this including applying a liquid resist by silk screening, applying a dry resist by laminating the resist material to the metal web, and applying a resist by electrophoretic deposition. These techniques do not necessarily provide a plated pattern having sharp definition and close location tolerances. Further, dry photo resists are much more costly than the non-conductive ink maskant of the present invention. Electrophoretic resists, while less costly than dry resists are still more costly than the present ink maskant. Also, electrophoretic resists can not be applied at speeds comparable with the present invention.
Another technique that provides improved plating definition uses a photo resist applied over the entire workpiece by one of the liquid resist, dry resist or electrophoretic deposition techniques. The photo resist is then selectively exposed by interposing a mask between a source of actinic radiation and the resist coated workpiece. This causes the exposed area to be more soluble in the case of a positive photo resist, or less soluble in the case of a negative photo resist when the workpiece is subsequently immersed in a developing solution. Such an electrophoretically applied photo resist technique is described in European Patent Application 0 507 043 A2. Again, electrophoretically deposited resists are more costly than the present ink maskants, and their process speeds are slower than the present invention.
Still another prior art process uses mechanical masks such as moving belts to produce stripes of electrodeposited material while the belt contacted portions of the substrate are left unplated. However, this technique is inadequate for producing thin, well defined stripes because fabricating very narrow belts and locating them accurately against the web to be masked presents many difficulties.
Accordingly, there is a need for metal web substrates that are electroplated in well defined, sharp and, if required, narrow stripes. In that respect, it is important that the unplated portions of the web are free of electro deposited metal, and the plated area transitions into the unplated area at a substantially perpendicular slope to the plane of the web. The masking apparatus and method of the present invention provide such a web substrate having well defined ink stripes applied thereto with precise boundaries and very little wander. Accordingly, important aspects of the present invention are that the applied ink maskant has extremely close width tolerances, very little wander along the length of the web and is laid down free of pinholes and like defects.
These and other aspects of the present invention will become more apparent to those skilled in the art by reference to the following description and to the appended drawings.